In data networks, devices are linked to one another via connections in order to interchange data with one another. With regard to the devices, a distinction is drawn between central devices, for example servers, and end points, for example PCs. End points such as these are frequently also referred to as clients. In general, the devices communicate with one another in data networks on the basis of allocated addresses. When the data is interchanged in a data network on the basis of the Internet Protocol, the addresses which are used are so-called IP addresses (IP=Internet Protocol).
Many data networks, in particular those with a large number of devices, are structured. This is necessary, for example, in order to reduce the network load and to ensure data protection in networks with a large number of branches. For structuring, the data networks are subdivided into logical subareas, which are also referred to as domains. Within one domain, for example, a number of PCs may be allocated to one specific server or to another central device.
One widespread embodiment of the described data networks is speech data networks, which are also referred to as VOIP networks (VOIP=Voice over Internet Protocol). Speech data networks also have central devices, for example gateways, gatekeepers and DNS servers, as well as end points (“clients”, “VoIP-clients”) which, in speech data networks, may, for example, be in the form of a telephone with a data network connection (“IP phone”), in the form of a multimedia PC, or else in the form of a PC with telephone emulation (“soft phone”). These end points or “clients” are also generally referred to as terminals, by analogy with line-switching telephony.
Before they are used, the devices in data networks must be configured in order to ensure disturbance-free operation. In the case of clients in speech data networks, by way of example, this means that these devices have to be set for the transmission and/or compression protocol (“Codec”) which may be used for speech transmission in the data network or data network element, and for the central device which may be used by the respective terminal, that is to say, for example, for the gateway which is allocated to the corresponding appliance, etc. In this case, the IP addresses of the central devices to be used must also be configured in the corresponding terminals, in order that the terminals can communicate with them.
The DHCP method (DHCP=Dynamic Host Configuration Protocol) is known for the configuration of computers (PCs) in data networks (for example: R. Droms, “Dynamic Host Configuration Protocol”, Request for comments: 2131, Brucknell University, March, 1997). The DHCP method is implemented with the aid of a central instance in a data network, which generally runs in the form of software on computer hardware and is generally referred to as a “DHCP Server”. The method is predominantly used in computer networks in which the availability of useable (free) IP addresses is short, or in those in which a large number of mobile computers are active at different times. In this case, from the limited range of available IP addresses, an IP address is assigned “on loan” only to those computers which are currently connected to the data network (“online”). For this purpose, after being switched on (“booted up”), a computer first of all sets up a connection to the DHCP server, and in the process requests the assignment of a free IP address. The DHCP server then assigns the computer an IP address—generally for a specific validity period—and the IP subnetwork mask that is required in that network segment, and also transmits to the computer the address of a DNS server (Domain Name System server) which can be used in this network segment.
In known data networks, it has been found to be disadvantageous that devices must be configured manually at regular intervals, which is associated with a large amount of labor effort. This is particularly true when an existing configuration has to be changed because, for example, a central device in the corresponding data network has changed its network address, or when central devices are added to the network, or are removed from it. Whenever the association between end points and central devices in the data network is changed, this results in the necessity to change the configuration of the end points in real time.
Although the use of the DHCP method as described above allows the configuration of devices with an IP address, an IP subnetwork mask and with the address of a DNS server, it is, however, possible only to a restricted extent with the known DHCP servers to transmit to the devices (computers) an amount of configuration data which is significantly greater than this “basic configuration”. As mentioned above, the clients in speech data networks, in particular, must be supplied not only with the “basic configuration” but also with a large number of other information items (parameters). Furthermore, although the DHCP method is able to assign a newly connected device a free IP address from the range of available free IP addresses, this is not intended to allow, for example, selection of a suitable gateway for a device from a number of gateways in a data network, and to assign this for use.
It is known for the association between end points and central devices (servers) to be updated automatically by the servers in a data network carrying out so-called “scanning” at regular time intervals. The aim of the “scanning” is to find end points which have been added to the network and to send all of the necessary information to these end points in order to configure them for operation in the data network. In this case, each server sends test messages to each address from a specific address range (“address band”) and thus checks whether the corresponding addresses have each been allocated to end points. The end points which are found in this process are then supplied with appropriate information, if they have not yet been configured, or have not yet been correctly configured, thus setting them up for operation in the corresponding data network.
With the “scanning method”, it has been found to be disadvantageous that the cyclic transmission of a large amount of test messages results in a high network load, to be precise even when only a small number of end points, or none at all, have been added to the data network. Those end points which have been newly added to the data network between two “scanning” processors cannot be used until the next run has been completed. A further disadvantage of this method is that the address structure in the data network must be designed such that the network addresses of the end points that have been added must be matched to the address bands which the corresponding servers search through or, conversely, the address bands must be matched to the addresses being used in the data network.